Calculate the mass of a cube of platinum of edge length 0.040 mm (the density of platinum = 21.4g/cm^3)?

Question

This is a question from an online homework assignment. My professor refuses to help me with it, saying that him helping would be like "helping me on an exam." The website I'm submitting it to keeps telling me I have the wrong answer, 1.4x10^-6 g

Please help me.

Answer 1

OK the density is given in g/cm³, so let us work in cm. length of side = 0.04mm which is 0.004cm.

Volume of cube = 0.004³ = 6.4*10^-8cm³

Density = mass / volume

Mass = Density * volume

mass = 21.4*6.4*10^-8

Mass = 1.37*10^-6grams

Make that 1.4*10^-6grams ( you had only 2 sig figures in the question.)

Answer 2

V = ( 0.040 )^3 = 0.000064 mm^3 => 6.4 x 10^-8 cm^3

mass = V x d = 6.4 x 10^-8 cm^3 x 21.4 g/cm^3 =1.4 x 10^-6 g